Origin and maintenance of diversity
Beginning in the mid 1980s, Rainey became intrigued by capacity of Pseudomonas isolates to diversify on agar plates and more spectacularly in static broth culture. A decade on he realised, on seeing diversification in spatially structured microcosms, but not in spatially unstructured environments — and prodded by a visit by Rich Lenski — that diversification was a response to ecological opportunity and akin to a miniature adaptive radiation. Joined at the Department of Plant Sciences by Mike Travisano as a post doc the two further developed further work culminating eventually in a seminal publication describing “Adaptive radiation in a heterogeneous environment”. One day Rainey will recount the long and winding road to publication.
The Pseudomonas radiation has proved a rich model for numerous studies by the Rainey team and beyond. Despite a great deal of study, there remains much to be learned, particularly concerning ecological interactions, niche construction and so forth. It was always Rainey’s hope that the system would be revisited and taken apart in a much more detailed and quantitative manner. That time, thanks to Loukas Theodosiou‘s presence and efforts is now here.
Loukas has established a quasi-chemostat system that maintains spatial structure while allowing continual replenishment of resources. In parallel, Andy Farr has constructed a bar-coded library of ancestral SBW25 that has been used to found replicate microcosms. Armed with this, we are now set to capture in fine detail the ecological and evolutionary dynamics of the Pseudomonas radiation over a time-frame of weeks (and not just days). One hope is that we will see evidence of the continuation of the non-transitive (rock-paper-scissors dynamic) interactions reported by Rainey & Travisano. But there will be much more than this!